Method for manufacturing alloy nano powders

ABSTRACT

A method for manufacturing alloy nanopowders is disclosed, which comprises a step in which a wire manufactured in such a manner that at least one hetero metal is coated on a metallic wire is used to manufacture alloy nanopowders. At least one hetero metal is coated on a pure metal wire or an alloy wire based on an electroplating method, an electroless plating or other methods. The alloy wire is electrically exploded for thereby manufacturing at least two-component alloy nanopowder.

TECHNICAL FIELD

The present invention relates to a method for manufacturing alloy nanopowders, and in particular to an improved method for manufacturing alloy nanopowders using a wire which is manufactured in such a manner that at least one hetero metal is coated on a metal wire.

BACKGROUND ART

Metal nanopowders are manufactured by an electrical explosion method, a plasma method, a liquid phase method, a laser ablation method or a vapor deposition method etc. With the above methods it is not easy to manufacture alloy or multi-component nanopowders. A production rate is also very low. However, the electrical explosion method may have a relatively faster production rate as compared to the other methods. With this method, it is possible to manufacture nanopowders of diverse pure metals, oxides and nitrides.

In the electrical explosion method, a high powder pulse of only a few microseconds duration is applied to a wire, which is fed into an argon-filled container. Under an impulse current of a very high intensity within a short reaction time, the metal wire is explosively convereted into a high-temperature vapor by the almost instantaneous discharge caused by energy release from a capacitor bank. With the current electrical explosion method, a wire with a diameter less than 1 mm (commonly 0.2˜0.6 mm wire) is used when manufacturing the powders.

In the case of pure metals, since a wire for the electrical explosion method has been commercially manufactured and available, there are not any problems for obtaining the materials. However, the alloy or intermetallic compound has some problems during its wire forming process as compared to the pure metals. Since alloy powders are mostly produced by small quantity batch production system, it is very difficult to obtain alloy wires of a specific composition in the market.

So, it is urgently needed to develop a method that alloy nanopowders can be manufactured without using alloy and intermetallic compound wires as a raw material so as to expand an application range of the electrical explosion method so that nanopowders of diverse alloy and intermetallic compounds are manufactured. As one of the methods, a plurality of hetero pure metal wires are concurrently inserted and exploded. However, this method has not been successful yet.

As an apparatus for manufacturing alloy nanopowders based on an electrical explosion method, there are Korean patent No. 10-0394390 (title: method and apparatus for manufacturing metal nanopowders based on electrical explosion method, registered on Jul. 30, 2003), Korean patent No. 10-0446956 (title: feeding apparatus of electrical explosion apparatus for nanopowder manufacture, registered on Aug. 24, 2003), Korean patent No. 10-0407160 (title: apparatus for manufacturing nanopowders, registered on Nov. 13, 2003), and Korean patent application No. 10-2004-0105378 (title: electrical explosion apparatus for nanopowder manufacture having thermodynamic and electrical stabilities, laid-open on Dec. 16, 2004).

However, as a method for manufacturing alloy nanopowders, there is only one Korean patent No. 10-0551547 (title: metal, alloy or ceramic nanopowder manufacture method based on electrical explosion method in which a plurality of wires are concurrently inserted, registered on Feb. 6, 2006). In this Korean patent, a plurality of hetero metal wires are concurrently exploded. However, the above method is not actually adapted for applications.

In particular, there are not disclosed a simple and low cost manufacturing method of alloy or intermetallic compound wires and an alloy nano powder manufacturing method by electrical explosion which does not use alloy or intermetallic compound wires.

DISCLOSURE OF THE INVENTION

Accordingly, it is an object of the present invention to provide a method for manufacturing alloy nanopowders without using alloy or intermetallic compound wires.

In the present invention, there is disclosed a method of using a wire manufactured in such a manner that at least one hetero metal is coated on a metal wire so as to overcome the problems related to the raw material wire for electrical explosion. Here, the metal wire represents a pure metal wire, an alloy wire or an intermetallic compound wire.

As a method of coating a certain metal or alloy on a metal wire, there are sputtering, evaporation, chemical vapor deposition, melt dipping, electroplating, and electroless plating methods, etc. Among the above methods, it is known that an electroplating method and an electroless plating method are capable of economically coating diverse metals. In addition, the electroplating method is capable of performing a continuous operation using a simple facility, so that the electroplating method may be automated in combination with the electrical explosion process.

Therefore, a wire manufactured in such a manner that at least one hetero metal is coated on a metal wire by electroplating method, and the manufactured wire is used as a raw wire for the electrical explosion method for thereby manufacturing alloy nanopowders. Here, the kinds and compositions of the alloy of the alloy nanopowders may be controlled by the combination of metals and thickness of coated metal layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become better understood with reference to the accompanying drawings which are given only by way of illustration and thus are not limitative of the present invention, wherein;

FIG. 1 is a schematic illustrating an electroplating apparatus adapted to the present invention;

FIG. 2 is a schematic illustrating an electrical explosion apparatus adapted to the present invention;

FIG. 3 is a photograph of a nickel-copper coating wire according to the present invention;

FIG. 4 is a X-ray diffraction (XRD) pattern of a nickel-copper alloy nanopowder manufactured according to the present invention;

FIG. 5 is a transmission electron microscopy (TEM) micrograph of a nickel-copper alloy nanopowder manufactured according to the present invention;

FIG. 6 is a X-ray diffraction (XRD) pattern of an aluminum-copper alloy nanopowder manufactured according to the present invention; and

FIG. 7 is a transmission electron microscopy (TEM) micrograph of an aluminum-copper alloy nanopowder manufactured according to the present invention.

MODES FOR CARRYING OUT THE INVENTION

With reference to the accompanying drawings, the method for manufacturing Ni—Cu and Al—Cu alloy nanopowders will be described.

FIG. 1 is a schematic illustrating a plating apparatus used when a coated wire is manufactured according to the present invention. A copper plating performed with respect to a nickel wire will be described as an example. A base metal wire 40 is hung at a wire support member 60 within a plating bath 10 filled with a copper plating solution 30 and is connected to the negative terminal of a DC rectifier 50, and a copper anode 20 attached to an inner wall of the plating bath is connected to the positive terminal. A DC voltage of about 1.2 volt is applied. Copper ions contained in the plating solution are attached to the surfaces of the nickel wire for thereby forming a copper coating layer. Here, the thickness of the copper coating layer is in proportion to the plating time and to the applied voltage (or current). Here, it is needed to mechanically reciprocate the wire support member 60 so as to agitate the plating solution and the nickel wire 40.

FIG. 2 is a schematic view illustrating an electrical explosion apparatus used for manufacturing nanopowders according to the present invention. The nickel/copper wire 70, which is manufactured in the same manner as the previously described manner, is inserted between two electrodes 90 and 100 through the roller, with two electrodes being provided in a chamber 80. The air of the chamber 80 is evacuated, and the chamber 80 becomes a vacuum state. Argon(Ar) gas is charged into the chamber 80. In this state, when a strong impact power is instantly applied, an alloying process and nanopowder process are performed at the nickel/copper wire 70 through melting, discharge and vaporization. The powders produced as electrical explosions are finished are collected in a glass bottle attached through a powder collecting part 110. The alloy nanopowder has a diameter of 100 nm or less than the same.

Embodiment 1

In this embodiment of the present invention, copper is plated using the plating apparatus of FIG. 1, and a nickel/copper wire is manufactured. Nickel/copper alloy nanopowders are electrically exploded in apparatus of FIG. 2 using the above wire.

Here, the copper plating solution is prepared using distilled water. The composition of the copper plating solution is 195 g/l of CuSO₄5H₂O and 30 g/l of H₂SO₄. The copper plating is performed at a room temperature, and the current density during the plating is about 10˜50 mA/cm². The nickel wire used as a base metal has a diameter of 0.2 mm. FIG. 3 is a photograph showing the appearance of the nickel/copper wire.

The plated nickel-copper wire is exploded at the electrical explosion apparatus. The electrical explosion apparatus is a product model NTI 10P manufactured by Nano technology corporation. The length of the wire used for the electrical explosion is 10 mm. The electrical explosion experiment is performed in a state that argon gas is filled in the chamber to about 3 atmospheres so as to prevent oxidation of nanopowders. After the electrical explosion is finished, a chamber lid is slightly opened, and a passivation process is performed so as to prevent burning due to the fast oxidation of the powders. The crystal structure, composition, size and shape of the powder are analyzed.

As a result of the analysis which is conducted concerning the type, size and crystal structure of the particle, the average particle size of the powder is within a range of 50˜100 nanometer on transmission electron microscope (TEM) micrograph. The powder has a nearly complete spherical shape.

FIG. 4 is a view illustrating a result of a X-ray diffraction analysis of nickel-copper alloy powder according to the present invention. A diffraction peaks of (111), (200) and (220) planes are between the values of nickel and copper indicating the powder has a single phase alloy. It is well known that Ni—Cu alloy has a mutual solubility. FIG. 5 is a transmission electron microscope (TEM) photograph of nickel-copper alloy. The average particle size is about 50 nanometer. The shape of the particle is almost spherical.

Embodiment 2

In this embodiment of the present invention, copper is electroplated on an aluminum wire in the same manner as the first embodiment of the present invention for thereby manufacturing an aluminum/copper wire. Aluminum-copper alloy nanopowders are manufactured based on the electrical explosion method using the aluminum/copper wire as a raw material.

Here, the aluminum wire has a diameter of 0.2 mm. The composition of the copper plating solution is 195 g/l of CuSO₄5H₂O and 30 g/l of H₂SO₄. The plating is performed at room temperature. The current density is about 10˜50 mA/cm². The plated aluminum-copper wire is exploded in the electrical explosion apparatus of FIG. 2. The explosion is performed under the same condition of the first embodiment of the present invention.

FIG. 6 is a view illustrating a result of the X-ray diffraction analysis of aluminum-copper alloy powders according to the present invention. As shown in FIG. 6, the major phases of the powders are CuAl₂, and Cu₉Al₁₄ with small amount of aluminum. FIG. 7 is a transmission electron micrograph of the aluminum-copper alloy nanopowders. Here, the average size of the particle is about 58 nanometers, and the shape of the particle is almost spherical.

When the present invention is actually adapted to the applications, the electroplating process may be performed in a continuous plating system. The whole powder-making processes may also be automated in combination with the continuous plating method and the electrical explosion process.

In the above, the present invention has been described in details. The disclosed descriptions of the present invention are not limited thereto. In addition, another method may be adapted except for the electrical explosion method.

In the manufacture of the alloy nanopowders according to the present invention, the wire coated with at least one hetero metal is used without using an expensive alloy or intermetallic compound wire which is difficult to obtain. In the present invention, it is possible to manufacture alloy nanopowders of diverse composition. The kinds and composition of the alloy can be easily controlled.

In the present invention, the manufacturing method is simple, and the manufacturing cost is low. A mass production may be possible, and a commercialization is easy. The whole processes may be easily automated in combination with the electroplating method, which is performed based on the continuous plating method, and the electrical explosion process.

As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described examples are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalences of such meets and bounds are therefore intended to be embraced by the appended claims. 

1. A method for manufacturing alloy nanopowders, comprising a step in which alloy nanopowders are manufactured using a wire which is manufactured in such a manner that at least one hetero metal is coated on a metallic wire.
 2. A method for manufacturing alloy nanopowders, comprising a step in which a plating process for coating at least one hetero metal on a metallic wire is performed based on a continuous plating process, and said plating process is performed in combination with an electrical explosion process. 